The present invention relates to an image-receiving element for heat transfer type dye image, more specifically to diffusion transfer type heat-developable light-sensitive material or an image-receiving element for heat transfer type dye image.
It has been known in the prior art to obtain color images by transferring dyes to image-receiving elements by heating For example, in the system known as diffusion transfer type heat developable light-sensitive material, color images can be obtained by transferring diffusible dyes, formed for image forming upon heat development, onto image-receiving elements in a heat development step and/or subsequent transfer step.
The above image forming method is described in, for example, Japanese Unexamined Pat. Publications Nos. 12431/1984, 159159/1984, 181345/1984, 229556/1984, 2950/1985, 52643/1986, 61158/1986, 61157/1986, 180550/1984, 132952/1986 and 139842/1986, U.S. Pat. Nos. 4,595,652, 4,590,154 and 4,584,267, etc.
In the system known as heat transfer system, color images can be obtained by heating heat transfer materials by a thermal head to transfer heat diffusible dyes onto image-receiving elements. By controlling thermal energy of the thermal head in this operation, gradation of images can be obtained.
The above image forming system is described in, for example, the specifications of Japanese Unexamined Pat. Publications Nos. 239289/1985, 22993/1986 and 63194/1989, etc.
In the above-mentioned methods, it is required that the dyes are thermally high diffusible in order to shorten the transferring time and facilitate reduction of thermal energy. However, if the dyes are designed to be high diffusible, image density will be lowered by retransfer of color images on the image-receiving elements thus obtained during storage, etc. thereby resulting in the defect of deterioration of fixing property.
As a technique for solving such a problem, the specifications of Japanese Unexamined Patent Publications Nos. 48765/1984 and 124337/1984 disclose the method in which fixing property can be improved by forming heat-diffusible dyes, which is capable of chelating, by heat development, transferring the dyes onto image-receiving elements and thereby forming chelated dye images in the image-receiving elements. The specifications of Japanese Unexamined Pat. Publications Nos. 78893/1984 and 2398/1985 disclose the method in which fixing property can be improved by heating light-sensitive transfer materials containing heat-diffusible or sublimatable, which is capable of chelating, dyes and thereby transferring the dyes to form chelated dye images in the image-receiving elements.
These methods are excellent in improvement in fixing property and stability of dyes to heat, light, etc. However, the image-receiving elements used for such systems includes the following problems.
More specifically, it is difficult to permit compounds, which supply metal ions to dyes (hereinafter, called as a metal source), to exist in image-receiving elements in a stably dispersed condition. Particularly, in the case of adding the metal source to hydrophobic binders, which are preferable binders when heat-diffusible dyes are received, uneven density of images and reduction of image quality of image-receiving elements were caused by precipitation and coagulation of the metal source. The method further include problems that a part of dyes remains in the unchelated state due to low rate of the chelating reaction, that white background portions are stained by coloring of the metal source, etc.